The Zodiac constellation of Sagittarius lies in one of the most exciting parts of the night sky. As a Zodiac constellation, Sagittarius gets regular visits from the planets, moon, sun, and even asteroids. It also floats in front of the center of our Milky Way galaxy. Rich star fields, clusters, nebula, and more are all found here.
Stars
Sagittarius can be found low in the south from summer through fall. Although it is supposed to represent an archer, an asterism in the constellation looks distinctly like a teapot. Look for the handle to be on the east side and the spout to be on the west side. The brightest star in Sagittarius is the star marking the bottom right corner of the teapot, Kaus Australis. Also known as Epsilon Sagittari, this magnitude 1.79 star lies 144 light-years away. The next brightest star is at the opposite end of the teapot, the top star in the handle, Nunki. Also known as Sigma Sagittari, this 2.04 magnitude star shines from a distance of 224 light-years. Most of the other stars in Sagittarius and 2nd and 3rd magnitude. The star marking the top of the teapot's lid is Kaus Borealis, a magnitude 2.82 star lying 77 light-years away. The stars marking the top of the spout are Alnasl, which marks the tip of the spout at magnitude 2.98 and 96 light-years away, and Kaus Media, which marks the spout's connection to the pot at magnitude 2.72 and 305 light-years away. The star at the bottom of the handle where it connects to the pot is Ascella, a magnitude 2.60 star lying 89 light-years away.
One other notable star that is not a part of the teapot asterism is the double star Beta 1 and 2 Sagittari. It lies 22 degrees directly under the tip of the teapot's lid and on the other side of the Southern Crown, Corona Australis, that nestles in next to Sagittarius. Beta 1 is also named Arkab and it is a magnitude 3.96 star 378 light-years away. Twenty-one arcminutes below that is Beta 2, a magnitude 4.26 star lying 138 light-years away.
Clusters and Nebulae
Star clusters are sprinkled all over Sagittarius, and many of them are quite bright. A chain of clusters dangles above the lid of the teapot. Starting at the top, M17, also known as the Swan Nebula or the Omega Nebula, is a cluster plus nebulosity and shines at 6th magnitude. One degree below that is M18, a magnitude 6.9 open cluster. Just over one degree below M18 is M24, a dimmer 11th magnitude open cluster known as the Little Star Cloud. Hopping three degrees to the left is M25, a bright magnitude 4 open cluster. Hopping the other way, five degrees to the right of M24, is M23, a magnitude 5.5 open cluster. Four degrees below M23 is a nice grouping of interesting objects. First is M21, a magnitude 5.9 open cluster. Less than a degree below that is the much-photographed Trifid Nebula, M20. It shines at magnitude 6.3. A little one and a half degree jump below that is another object frequently photographed, M8, the Lagoon Nebula. M8 is magnitude 5.8. Can you see the dark dust lanes cutting through both M8 and M20?
Seven relatively bright globular clusters lie in Sagittarius. M28 is just one degree above the top of the teapot and shines at magnitude 6.9. Three degrees to the left is M22 at magnitude 5.09. Down in the bottom of the teapot lie three globular clusters. From left to right they are M54, M70, and M69. They are magnitudes 7.7, 8.1, and 7.7 respectively. Eight degrees below the handle of the teapot is M55, a magnitude 7 globular cluster. And lastly, M75 is a magnitude 8.6 globular cluster lying over 14 degrees east of the handle, on the border with Capricornus.
Planets
Planets pass through Sagittarius all the time, but Pluto is currently making its home there. From late 2007 it can be found in the upper right borders of Sagittarius. It is slowly making its way across the upper part of the constellation, heading east, where it will exit the constellation and enter Capricornus on New Years' Day, 2024.
The images of M2, M72, and the Helix are courtesy of Calvin College Observatory.
